By looking at stroke data spanning a decade, Finnish researchers have found a link between daylight saving time and a short-lived increase in some people's risk for stroke.
Although the findings of the study, which is to be presented at the annual meeting of the American Academy of Neurology in Vancouver, Canada in April, do not prove that the changing clock is to blame for increased incidence of stroke, Turku University Hospital neurologist Jori Ruuskanen said that it is difficult to imagine other factors that can explain the pattern.
Ruuskanen also said that there is already a known association between stroke risk and the disruption of the circadian rhythm, the shift on the biological processes of the body over a period of 24 hours in response to light and darkness so they wanted to know if daylight saving time may be putting people at risk for ischemic stroke.
Ischemic strokes, which are caused by a blood clot in an artery that supplies the brain, accounts for 85 percent of all stroke cases, according to figures from the American Stroke Association.
Ruuskanen and colleagues looked at the incidence of stroke in more than 3,000 individuals who were admitted to the hospital during the week after a daylight saving time transition and the incidence of stroke in a group of nearly 12,000 people who suffered from stroke two weeks prior to or two weeks following the week of transition.
They found that the overall rate of ischemic stroke was up by 8 percent during the first two days following a daylight saving time transition albeit no difference was found after two days.
The study likewise found that cancer patients had 25 percent increased odds of having a stroke after daylight saving time than during another period. Older adults who were over 65 years old and above also saw a 25 percent increased risk for stroke right after the transition.
Experts said that some planning may help people reduce sleep disruptions, which are known to cause an array of unwanted health conditions.
"It may be generally helpful to adjust gradually to daylight saving time rather than all at once," said Andrew Lim, from the Sunnybrook Health Sciences Center, in Toronto.